Leetcode: Bitwise AND of Numbers Range


Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive.

For example, given the range [5, 7], you should return 4.

有些难度，一定不是O(n)的方法。如果M不等于N，那么最后一位一定有0和1，可以清0，移位一直判断这个。

class Solution {
public:
int rangeBitwiseAnd(int m, int n) {
int shift = 0;
while (m != n) {
m >>= 1;
n >>= 1;
++shift;
}

return m << shift;
}
};